Requirements:Wayward SonYou'll get this quest during the Wayward Son quest. To get it, you need to find Thrask's Letter on the body of an Abomination in Arthuris's Private Dock during the quest. Basically it consists of delivering the letter to Thrask.

You have two options, you can give him the letter and gain XP, or you can make him pay for it and get gold (5 sovereigns). Keep in mind that if you blackmail him, he won't be very agreeable in the Act of Mercy quest later, which could complicate things depending on how you want to play it. You also get a companion boost with everyone except Fenris if you hand it over for free.